Suction devices of the type referred above are already known. For example, devices are known which provide a connection conduit between said trapping mouth and said yarn suction conduit which has a winding and complex configuration, aimed at creating a vacuum in an area upstream of said trapping mouth by injecting pressurised air into the secondary connection conduit mentioned.
Said device is disadvantageous in various respects. Above all it has an excessively complex configuration which entails appreciable manufacturing costs. Moreover, said known device has the disadvantage that a considerable quantity of pressurised air has to be supplied to be injected inside the winding connection conduit with the aim of creating a sufficient suction pressure inside said conduit such as to aspirate the yarn towards the main vacuum conduit.
This entails the use of considerable quantities of compressed air, compressed up to a high pressure value. Said use is too onerous, both due to the excessive use of energy for compression and due to the cost of the relevant compression equipment to be made available for compressing such considerable quantities of air.
The use of such a device also involves a disadvantageous drop in the vacuum pressure inside said main suction conduit. This disadvantage is even more damaging inside textile machines wherein a main vacuum suction conduit is connected to several yarn trapping mouths. The drops in vacuum pressure caused by injecting compressed air lead to a considerable drop in the pressure inside said main conduit with resulting malfunctioning of the yarn suction which may even totally eliminate the suction pressure thus making it impossible to use the suction system itself.
With the use of such a type of device for controlling suction inside yarn suction systems in textile machines, on the one hand either the number of trapping mouths which can be connected to said main conduit has to be limited, restricting the flexibility of use of the suction system, or, on the other hand, the value of the vacuum pressure applied inside the suction system has to be forced to increase, again with the need to use excessive quantities of energy for the appropriate equipment which creates said vacuum, the latter having to be more powerful and sophisticated and hence more expensive.
The object of the present invention is that of providing a yarn suction device for textile machines which avoids the disadvantages presented by known devices. More particularly the object of the present invention is to provide a device for yarn suction in textile machines which, although actuated by a pressurised fluid, avoids the use of excessive quantities of compressed air of known devices.
Another object of the present invention is that of providing a device for yarn suction in textile machines which has a simple structural configuration with low cost.